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Audio Valve Nut
DIY Champ
DIY Champ
May 19, 2022
In Show and Tell
Hi, just an update how things are going, Had to change a BASS driver in my main system due to distortion caused by a badly re-foam attempt by somebody else. Got to listen to music (Loudly ) in the work shop as I potter about. Before After I have two pair's of these HB1's, both were fairly cheap , 1 pair with a rubbing cone and a bad re-foaming job for the other. The bad re-foaming pair sounded the best !!!! . Deeper richer sounding. Changed the driver with the rubbing voice coil. Had to change the other driver in that pair to balance out the sound. Lucky I had a driver left over that I could use. Both pairs do not sound as good even when replaced with the correct driver's from manufacturer. Tim Mellow 25W Slow progress so far on the Tim Mellow 25W amp so far, still having issues with getting all the components. D1-D4 FR605G main rectifier's no stock available from all the major supplier's , looks like long delivery times they or have gone obsolete. Managed to get hold of some FR607G's same spec with higher PIV (1000V) so they will have to do. No luck sourcing 1k/10k 20 turn preset pot's can only find 10 turn pot's so far. Thought I would start building the power supply as I am eager to get this Amp up and running. Possible Capacitor layout to start with. Added Aluminum U channel bar for support for the chassis as 8-10kg of weight from the transformers was slightly bowing chassis.Used the U bar to fit the Tag board to so I will be able to build the power supply out of the chassis and test before other components are fitted. Possible position Using Tag Board to fit the capacitors Cap's soldered to Tag Board AO9 Did not like the color of the face plate for the A09 , light orange/yellow ??? so I decided to polish off the anodized color. Just a rough polish so far it looks great . Hope to get a mirror finish when finished. Finding a place for the VU PCB and transformer, PCB 9V AC supply needed, should of checked before purchasing , only 5v, 6.3v and 315v supplies available with the A09 so had to get extra transformer . Only place available that could accommodate Transformer and PCB , tried a better capacitor (replaced with a 270uf 500v) for the B+ instead of the Chinese cheapo. Must check dimensions next time just slightly too big to fit in available space. Replaced Main's On/Off switch with a better one. Shaft spline broke after fitting knob. Thought I would check resistance of the Pot I got for the Skunkie Tube Headphone project and 25w Amp Pot. If you don't check the components before you install them I would from now on. It seems the quality is not what it used to be back in the old days. Keep Up The Good Work Skunkie Stay Safe Will
Tim Mellow 25W OTL / AO9 Update content media
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Audio Valve Nut
DIY Champ
DIY Champ
Apr 11, 2022
In Show and Tell
Just found some good information from the Hammond Transformer web site. Helpful when you need to design a power supply for your project. Supplies information on what type of rectification and smoothing used to get Voltage and Current that you may require with the input voltage. Web Site: https://www.hammfg.com/electronics/transformers/rectifier?referer=968 Stay Safe and Well Stephe Have a good rest Will
Power Supply Design / Information content media
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Audio Valve Nut
DIY Champ
DIY Champ
Mar 28, 2022
In Show and Tell
(Added Video Files of meter's working , unable to load in the original Red Plating Post) Tim Mellow - 25W OTL Tube Amplifier Build / Progress Just got some more kit that I may use for this Amp. All holes for Tube bases Done. Chassis now formed using my home made sheet metal bender. Seen this Double VU Meter with driver board on Ebay , ooh, thought I'll incorporate it in the design. Original design had 2 x 1Amp meter's for biasing only, no VU Meter's. I have read in some of the forums these meter's were replaced by resistors and not fitted after initial set up. I'm going to use a switch were I can switch between the resistors and meters so as to check the biasing now and again when needed. Trying to fit the 1 Amp meters any where on the chassis just did not look aesthetically right. Hole cutout for the Meter, took about an hour to complete , took extra care not to mark the chassis as this will be in full view when complete. Deciding were the I/P'S and O/P'S are going. Final Placement Decided on this layout in the end. I ordered a pair of these with driver board some time ago to go with the Boyuurange A09 No Lamp adjustment with this PCB Dam Big Holes to drill in the Face Plate Made the mistake of measuring the resistance of all the meters and testing their deflection. 2 Pairs and I Double all varying resistances and deflections with the same current.The only consistency with parts from China is the Inconsistency. Best use these as "Indication Only" as they look like 20-30% variation between then. Having in the past calibrated Medical equipment these would be a nightmare to calibrate correctly and would be scraped but we'll use just to show some indication. Tested using another PCB with lamp adjustment Low level adjustment High level adjustment Blue meter's Illuminated Added Some Tape for better affect Chassis Size comparison to the Boyuurange A09 Giving the Meters workout Take Care and have fun. Will.
Progress on Tim Mellow 25W OTL Tube Amplifier content media
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Audio Valve Nut
DIY Champ
DIY Champ
Feb 24, 2022
In Show and Tell
This is the sound of one of the tubes Red-plating in a Chinese Amp. The tubes were all Chinese so I replaced the output tubes with Russian matched pairs and got a better sound from the mid rage with a little less Bass a response that I was not happy with. So I ordered 8 of the Russian equivalent tubes (6P1P) and swapped out the matched pairs and the sound was better. Still lacking low end Bass though , So I thought I would change the Pre-amp tubes for General Electric 6U8A'S and what a difference that made. Overall the amp now sounds much better, more uniformed across low mid and top frequencies with real punchy Bass. The Chinese tubes lasted about 18 months which is not bad as I use this amp in my workshop at 3/4 volume (4/5 with Jimmy Hendrix playing Live) while redoing my test setup and building other amps. Chinese Amp came all built up but then I went and Bought the Boyuurange A9 in kit from as it was so cheap. Thought I would see the difference between Class A/B and Class A output stages. I completed the build and tested. This amp sounded terrible . The mains Hum was very loud with no Bass . Dam Chinese rubbish . I preceded to find out were the Hum was coming from and found out that were the tubes are mounted there was no Ground at the metal plate that the tubes are all mounted on although the plate is secured with bolts to the main chassis . I grounded the plate and this made no difference. I then added 100ohm virtual grounding resistors to the heater supply to the output tubes , still no difference . Then I added 100ohm Virtual grounding resistors to the driver tubes and this the cured the problem. I took off the grounding resisters to the output tubes and this had no effect. The amp now sounds better but still not there yet. Tried 0.22uf and 0.33uf instead of the 0.1uf coupling Capacitors on the inputs, getting better then the Transformers and tubes arrived for my next project so work on this amp has been side tracked. Next project is the Tim Mellow 25W OTL Tube Amplifier with the Russian 6C33C , Dam these are Big tubes. Having some sourcing issues to get all the parts but got about 90% of what I need so far. Started making the chassis from sheet aluminum , Dam big holes for those tube bases. If you are in Europe I have found a source for transformers , Troidy in Poland . Sourced the Russian tubes from the Ukraine , Ironic with whats going on there at the moment, just got them before all this started. I now have Digilent Analog Discovery 2 so will Test all my amps and start a library of tests for people to reference .(Once I sort out /re jig my set up , DAM can't stop building Tube Amp's ) Keep Safe Will no earthing to main Chassis Tim Mellow's 25W OTL Tube Amplifier Going Slightly Different Layout Troidy Web Site Size comparison of the mains transformer to the A9 (got to pick up with two hands) The Parts
The Sound Of Red-plating content media
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Audio Valve Nut
DIY Champ
DIY Champ
Dec 03, 2021
In Show and Tell
he Audio Valve Nut - Trials and Tribulations of setting up An Audio Test Bench Hi, Will from the U.K. Just a bit of my background before we start: Electronics Technician for the past 27 years, worked for British, French, American, Japanese and Korean Electronics Companies and the Medical Industry. While in Collage studying, a few of the lecturers were in their 60’s and were from the 40-50’s era and said Valve Amplifiers were by far the best compared to the Semiconductor Amplifiers. So, I said to myself, one day I will build a Valve Amplifier and find out. There are many good semiconductor amps about but are 5-10 times the price. I like to listen to music reasonably loud and started to notice the harsh clinical sound with semiconductor amplifiers and that were getting irritating to listen to. May be an age thing? That day has now come to build that Valve Amplifier. I decided to start collecting equipment over the last couple of months to set up an Audio Test Bench. Started browsing over the internet for good Stereo HIFI circuits or built Valve Amplifier’s. Built Amps expensive, need a large jump in faith to go that route. May need to try out may different amplifiers, Speakers, combinations, and other equipment and match it up to get a good system. Looked at a few Chinese Amps online but hearing about quality/ warranty issues decided to look for circuits and build a proven design. Found Blueglow Electronics online hosted by Mark, saw his KT88 Amp build and thought that will be a good place to start. Started sourcing parts and found the O/P transformers from Edcor are almost twice the price here in the UK. Found Hammond supply a suitable replacement but on further investigation they have a dip in the frequency response at about 18khz. I probably would not notice as my top end hearing is not that good anymore. If I’m going to build an Amp, I’m going to build the best I can. Then found “Skunkie”, watched all the videos and enjoyed them. Nice to see somebody who can Solder Correctly, it’s quite common to see people even in the trade who can’t Solder correctly. Keep up the Good Work with the Videos and Instructions. Decided to buy a cheap 12W Per Channel Chinese Valve Amp just to get started so I could start testing speakers while searching for designs I could get all the parts for. Tested about 10 pairs of speakers so far, got 3 good pairs so far. 1 pair for the workshop, 1 as a spare and 1 for the living room. The others may be good with other Amps/setups but 1 or 2 were not good at all for top brands. For a cheap Chinese Amp. the sound is quite good with the right speakers, now I’m listening to the sound stage and can hear changes / variations in how the music has been mixed, live is amazing with the right recording. Quality is far better than Quantity. Oh My God , I have turned into an Audiophile.(Looks like I have always been an Audiophile but didn’t know it) . Just purchased another Chinese Amp (so cheap, It would cost that much just for the transformers and the case alone) but this one is an EL34 Single Ended Output just to see the difference between the types of O/P’s to see which one I prefer. OOOPPSS falling further down the Audiophile Rabbit hole. Also I want to try an experiment with it, Use their components and then use quality components and see if there is a marked difference. Getting close now to completing equipment acquisition to set up the Audio Bench. Around Christmas time I will re design my current setup for a proper Audio Setup ready for some proper testing/experimenting. Bring on the Tube Rolling. Attached are a few Trials and Tribulations on the way. (If you want to see more I’ll do a part 2 Just let us know). The Trials And Tribulations in a Nut Snell
Trials and Tribulations content media
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Audio Valve Nut
DIY Champ
DIY Champ
Oct 27, 2021
In Questions & Answers
Will from the UK, Can anybody tell me what the Minimum/maximum speaker impedance that can be tested with the Analog Discovery 2 as I need to test A Single-Ended OTL Headphone Amp that I am currently building ? HeadWise https://headwizememorial.wordpress.com/2018/03/20/a-single-ended-otl-amplifier-for-dynamic-headphones/
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Audio Valve Nut

Audio Valve Nut

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